The present invention relates to a method for the continuous measurement of the degree of intermingling of yarns and to a suitable measuring apparatus therefor.
Their cohesion is of decisive importance for the further processing of yarns. In the production of yarns, yarn cohesion is obtained for example by twisting, or by intermingling the individual filaments in jet nozzles. Intermingling is a particularly economical measure. However, it does not produce completely uniform yarn cohesion over the entire length of the yarn, but leads to the formation of individual more or less regularly spaced-apart intermingled places where the filaments are closely bonded together, and looser, bulkier areas in between of low yarn cohesion. This structure on the one hand confers a particular textile overall appearance on the yarns, but on the other also affects their further processibility.
The prerequisite for any non-damaging and problem-free further processing of intermingled yarns is that the intermingled areas are sufficiently close together. Missing intermingled areas have an adverse, in certain circumstances even catastrophic, effect on fabric quality and loom. It is therefore of particular importance to monitor the uniformity of the intermingling continuously.
One problem with the monitoring of yarn intermingling and the detection of non-intermingled areas (yarn bulges) is that any tension applied to the yarn serves to thin out and hence to disguise the non-intermingled areas, which makes their detection very difficult.
At present, four methods are used in industry for detecting non-intermingled areas in weaving counts:
(1) Visual examination by an experienced yarn examiner ("water test") In this test method, described in DE Offenlegungsschrift No. 2,901,165, yarn sections are introduced without tension into a water-filled vessel having a dark floor and the intermingled areas are then detected visually. Even if this visual assessment were replaced by an automatic optical apparatus, this water test would remain unsuitable for continuous measurement. PA0 (2) Further merely batchwise test methods are the needle test and the falling hook test, based on the same principle described in U.S. Pat. No. 2,985,995. PA0 (3) A continuous electrostatic test method is described in "Chemiefasern/Textilindustrie" (1978) page 788 et seq. In this method, the yarn is subjected to the impingement of a high electric charge and then guided through a grounded tube, and the filament spreads out considerably in the non-intermingled areas. The consequently more prominent yarn bulges can then be counted with a light barrier along which the yarn is passed. This method requires a relatively complicated measuring means and again only works satisfactorily if the yarn tension is not too high. PA0 (4) In mechanical sensing methods, which hitherto have permitted the highest yarn speed, the intermingled yarn is pulled through a gap between a stationary abutment and a force- or distance-recording sensing head supported by and liftable off the abutment. An instrument of this class is described for example in "Chemiefasern/Textilindustrie" volume 36 (1986), page 99 to 103. These instruments utilize the fact that the intermingled yarn sections cannot be pressed as flat as the non-intermingled yarn sections. The intermingled areas therefore exert a greater force on the sensing head than the non-intermingled areas.
An unsatisfactory feature with all four methods is the very low test speed. The yarn cannot be analyzed at a transport speed of more than 10 meters per minute (in the case of mechanical sensing). The production speed, however, is in general several hundred meters per minute. For this reason, the measurement of the degree of intermingling is at present possible only batchwise.